Linux bash: Multiple variable assignment
First thing that comes into my mind: read -r a b c <<<$(echo 1 2 3) ; echo “$a|$b|$c” output is, unsurprisingly 1|2|3
variable-assignment
What can I do with a moved-from object?
17.6.5.15 [lib.types.movedfrom] Objects of types defined in the C++ standard library may be moved from (12.8). Move operations may be explicitly specified or implicitly generated. Unless otherwise specified, such moved-from objects shall be placed in a valid but unspecified state. When an object is in an unspecified state, you can perform any operation on the … Read more
What does the keyword Set actually do in VBA? [duplicate]
set is used to assign a reference to an object. The C equivalent would be int i; int* ref_i; i = 4; // Assigning a value (in VBA: i = 4) ref_i = &i; //assigning a reference (in VBA: set ref_i = i)
Assign multiple columns using := in data.table, by group
This now works in v1.8.3 on R-Forge. Thanks for highlighting it! x <- data.table(a = 1:3, b = 1:6) f <- function(x) {list(“hi”, “hello”)} x[ , c(“col1”, “col2”) := f(), by = a][] # a b col1 col2 # 1: 1 1 hi hello # 2: 2 2 hi hello # 3: 3 3 hi … Read more
Global variables in R
As Christian’s answer with assign() shows, there is a way to assign in the global environment. A simpler, shorter (but not better … stick with assign) way is to use the <<- operator, ie a <<- “new” inside the function.
R: += (plus equals) and ++ (plus plus) equivalent from c++/c#/java, etc.?
No, it doesn’t, see: R Language Definition: Operators
Why is x == (x = y) not the same as (x = y) == x?
== is a binary equality operator. The left-hand operand of a binary operator appears to be fully evaluated before any part of the right-hand operand is evaluated. Java 11 Specification > Evaluation Order > Evaluate Left-Hand Operand First
Multiple left-hand assignment with JavaScript
Actually, var var1 = 1, var2 = 1, var3 = 1; is not equivalent to: var var1 = var2 = var3 = 1; The difference is in scoping: function good() { var var1 = 1, var2 = 1, var3 = 1; } function bad() { var var1 = var2 = var3 = 1; } good(); … Read more
What is the difference between shallow copy, deepcopy and normal assignment operation?
Normal assignment operations will simply point the new variable towards the existing object. The docs explain the difference between shallow and deep copies: The difference between shallow and deep copying is only relevant for compound objects (objects that contain other objects, like lists or class instances): A shallow copy constructs a new compound object and … Read more
How to assign from a function which returns more than one value?
(1) list[…]<- I had posted this over a decade ago on r-help. Since then it has been added to the gsubfn package. It does not require a special operator but does require that the left hand side be written using list[…] like this: library(gsubfn) # need 0.7-0 or later list[a, b] <- functionReturningTwoValues() If you … Read more